扬子西缘荥经地区三叠纪碎屑物源分析
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本文为深地资源勘查开采项目(编号:2019YFC0605202),国家自然科学基金资助项目(编号:41302080)和中国地质调查局项目(编号:DD20201173)的成果


Provenanceanalysis of Triassic sediments in the Yingjing area on the western margin of the Yangtze Craton
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    摘要:

    扬子西缘早三叠世处于伸展环境,而晚三叠世为前陆盆地。扬子西缘三叠系保存较好,是研究三叠纪构造转换物源响应方面的理想场所。本文根据重矿物电子探针和碎屑锆石测年,分析三叠系的物质来源,进而探讨与构造环境的对应关系。电气石探针结果显示,下三叠统主要源自贫锂花岗岩类伴生伟晶岩和细晶岩、变质板岩、变质砂岩、钙质硅酸盐岩和电气石石英岩,上三叠统主要来自贫锂花岗岩类伴生伟晶岩和细晶岩、贫钙变质板岩、变质砂岩和电气石石英岩,且自下三叠统至上三叠统变板岩和变砂岩的物源区比重逐渐增加;尖晶石显示,下三叠统砂岩主要来自大火成岩省、洋岛玄武岩和岛弧玄武岩类,上三叠统主要来自岛弧玄武岩类。碎屑锆石U-Pb测年结果表明,早三叠世碎屑锆石峰值为251~265 Ma、460~535 Ma和544~987 Ma,晚三叠世碎屑锆石峰值为228~251 Ma、255~387 Ma、429~523 Ma、573~954 Ma、1720~2004 Ma和和2453~2494 Ma。综合分析表明,下三叠统沉积物主要来自峨眉山玄武岩、康滇古陆,少量来自南秦岭造山带,而上三叠统的物源区主要为峨眉山玄武岩、康滇古陆、秦岭造山带和华北板块。三叠系物源的差异,主要与晚三叠世秦岭造山带与扬子板块碰撞有关。

    Abstract:

    The western margin of the Yangtze Craton was an extensional setting in the Early Triassic and a foreland basin in the Late Triassic.The well-preserved Triassic sediments on the western margin of the Yangtze Craton are ideal targets for studying the sedimentary provenance response to tectonic transformation.Methods:Based on the geological work,the heavy mineral electron probe microanalysis and detrital zircon U-Pb dating were carried out on the Triassic sandstones in this paper.Results:The results of tourmaline electron probe microanalysis show that the Lower Triassic sediments are mainly derived from the granitoids and their associated pegmatites and aplites,metapelites and metapsammites,calc-silicate rocks,and quartz—tourmaline rocks,while the Upper Triassic sediments are mainly derived from the granitoids and their associated pegmatites and aplites,Ca-poor metapelites and metapsammites,and quartz—tourmaline rocks.The proportion of metapelites and metapsammites gradually increases from Lower Triassic to Upper Triassic.Spinel results show that the Lower Triassic sandstones are mainly from large igneous provinces,oceanic island basalts and island arc basalts,while the Upper Triassic sediments are mainly derived from island arc basalts. Detrital zircon U-Pb dating results show that the Early Triassic detrital zircon peak is 251~265 Ma,460~535 Ma,and 544~987 Ma while the Late Triassic detrital zircon peaks are 228~251 Ma,255~387 Ma,429~523 Ma,573~954 Ma,1720~2004 Ma and 2453~2494 Ma.Conclusions: Comprehensive analysis show that the sediments of the Lower Triassic were mainly from Emeishan basalt,Kangdian Oldland and secondary from South Qinling orogenic belt.However,source areas of the Upper Triassic are mainly Emeishan basalt,Kangdian Oldland,Qinling orogenic belt,and North China plate.The differences of provenance in Triassic are mainly related to the collision between the Qinling orogenic belt and the Yangtze plate in the Late Triassic.

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张英利,贾晓彤,王坤明,王宗起,陈木银.2021.扬子西缘荥经地区三叠纪碎屑物源分析[J].地质论评,67(2):67030021,[DOI].
ZHANG Yingli, JIA Xiaotong, WANG Kunming, WANG Zongqi, CHEN Muyin.2021. Provenanceanalysis of Triassic sediments in the Yingjing area on the western margin of the Yangtze Craton[J]. Geological Review,67(2):67030021.

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  • 收稿日期:2020-12-07
  • 最后修改日期:2021-04-12
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  • 在线发布日期: 2021-04-20
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